Examining the Benefits of Unique Coloration for Male Trinidad Guppies

The predispositionof organisms in seeking certain phenotypic traits in mates is an oft-observed aspect of the natural world, with sexual selection being a well-studied phenomenon. However, unique coloration specifically often seems to be more linked to lessened survivability (due to an inability to camouflage in environments), or phenomena such as aposematism, where unique colors serve as a warning for predators. In a recent issue of Behavioral Ecology, a group of scientists detailed their work with wild guppies of both sexes and their observations of female guppy predisposition towards unusual male guppy coloration. As part of their background research, the researchers understood that the species Poecilia reticulata, also known as the Trinidad guppy, displays a sex-specific form of selection known as negative frequency-dependent selection (NFDS), under which atypical genotype and phenotype lead to increased fitness, with unique coloration being a beneficial and heritable trait.

Unlike previous experiments which utilized guppy populations brought up in the lab setting, Valvo’s team collected guppies from locations near six Trinidadian river drainages, such as spatially distinct pools, with the areas including differential levels of predation so that more than one predation regime was present. They were then transported to the William Beebe Tropical Research Station for observation. Related to this, the researchers sought to explore whether female fish originating from a natural environment would display greater in interest in uniquely colored male fish from the same source environment. In addition, they sought to determine whether different guppy populations yield different results and if predation regime and female choice were connected.

Male guppies were categorized in terms of coloration that was unfamiliar, rare, or common, with corresponding measurements being determined via quantitative, software based analysis. Female behavior in response to males was observed in terms of their swimming, lack of motion, whether they were facing the males, etc, with analysis carried out using linear mixed models. It was observed that females spent more time paying attention to males that had unfamiliar and rare color patterns, and males whose color patterns incorporated more orange and that were larger in size.

It was concluded that female guppy preference for uncommon male guppy coloration is probably a driver of genetic diversity. In terms of further research, the scientists recommended that factors such as the prevalence of male courtship also be taken into account during experimentation.